Despite being besieged by government troops, Islamist rebels have managed to eject ISIS from four areas in the Damascus region in a drive launched three weeks ago, the Observatory and rebel sources said.

ISIS was initially welcomed as a potential ally in the revolt, but the group’s fanaticism and treatment of civilian populations and all other insurgent groups sparked a sustained counteroffensive.

The Observatory said ISIS fighters have been expelled from Misraba and Maydaa, two towns in the eastern Ghouta of Damascus, as well as the suburbs of Yalda and Beit Sahm, just south of the capital.

In Yalda, the Observatory said, ISIS fighters turned themselves over to the Nusra Front, the Al-Qaeda affiliate in Syria, after securing two pledges: That they would be referred to a Shariah court, and that they would not be subjected to demeaning treatment.

It said that two were brothers of an ISIS commander, while a third was a wounded commander with the group.

“For us, there was no choice but to fight ISIS,” said Capt. Abdel Rahman al-Shami, a spokesman for the Islam Army militia, which is spearheading the offensive. “It was in self-defense. We are in a suffocating [regime] siege. We are fighting the regime, while ISIS is shooting us in the back,” Shami said.

“Now, they no longer have any official bases in eastern Ghouta. But we are chasing the remnants of ISIS,” he told AFP via the Internet.

Unconfirmed reports said a Kuwaiti national who was ISIS’ commander for the southern Damascus region, Abu Dujana, detonated his explosive vest when he was cornered by the rebel fighters.

In Aleppo province, a warplane bombed the ISIS-held town of Al-Bab but the strike apparently killed civilians – a man, a woman and five children, according to the Observatory. Other anti-regime activists, based in the city, said 12 people were killed and 30 injured in the strike.

On another front in rural Aleppo, five ISIS fighters were killed in clashes with the Kurdish YPG militia, which suffered two fatalities in the fighting, the Observatory said.

Meanwhile, ISIS is selling oil and liquid gas products extracted from fields under its control in Syria to Iraqi businessmen across the border.

“Each barrel of oil is sold to Iraqi businessmen for $20 to $40,” compared to more than $100 a barrel on global markets, Abdel-Rahman said.

ISIS last week seized the Shaar gas field in central Syria, and Monday saw clashes between regime troops, who had brought in reinforcements, and ISIS militants trying to maintain their hold on the facility.

In the town of Morek in Hama province, amid a weekslong standoff, rebels targeted several regime positions, but no information was available about casualties. In southern Syria, the army and rebels clashed in Deraa province, killing 12 opposition fighters, including a commander, the Observatory said.